Production of white lead



Aug., 6, 1929UI F. r1'. BAILEY ET AL PRODUCTION OF WHITE LEAD Filed June22, 1926 wA Tfn ,1c/00M rfa w/rhI Acfr/c 4cm ANU l awnfnfa ffm oma/s HIM/N/ J6' warf/P A c/aum rsa 'Il llHUllllll lll Patented lling.. d, i929..

A T e FRANK T. BAILEY AND WILSON AUSTIN, OIF NEW YORK, N. Y.

PRODUCTION F WHITE LEAD.

Application filed June 22,

rihis` invention. relates to the production ot white lead and has for anobject to'produce White lead of superior quality in a more expeditiousand economical manner than heretofore.

According to the invention, powdered anhydrous lead oxide or litharge ispassed through a corroding atmosphere of aqueous vapors, acetic acid andcarbon dioxide gas.

Preferably this is accomplished by introducing a mixture of acidulatedwater and powdered 4lithargc into a tank having an outlet at its bottomleading to a pump, the discharge of which is connected to a nozzlearranged Within the tank so that liquid drawnY out of the tank issprayed through the upper portion of the chamber and allowed to drainback to the bottom of the tank. While the mixture is being thus sprayed,carbon dioxide gas is passed through the tanky in such a manner that themixture and gas are brought into intimate contact.

In this process the litharge is converted into white lead without theformation of any a5 appreciable stable intermediate products. Instead offorming hydrated lead acetate Whichis then converted by carbon dioxideinto White lead, as in the former processes, it appears that yaccordingto this process the acetic acid or other equivalent hydrating agentforms a hydrated particle, but this action taking place as it does in acarbonating atmosphere is not completed to the extent of forming theacetate or other hydrate. In other words, .in the preferred method theacetic acid converts the litharge into hydrated lead oxide, but thecarbon dioxide having a greater affinity tor this hydrated particle thanhas acetic acid, the carbonate is formed with this particle instead ofthe acetate. The present process requires only `one-halt' to one percent of pure acetic acid by weight ot' the litharge used asdistinguished from the 10% by Weight or more previously used.

By starting the process with thoroughly oxidized lead, the corrosion. isnot delayed pending the oxidation of metallic lead which process is veryslow at the low temperature necessary to permit hydration7 and there isn o possibility of there being any finely divided particles or'unoxidized lead in the finished product to aiect its color. By usingpowdered litharge, no attrition or grinding 1926. Serial No. 117,677.

off of particles or eatingv in by corroding agents is necessary. Thewater is used as a mechanical means or carrying agent for the lead oxideparticles, so that it is possible repeatedly to diffuse them through thecorroding atmosphere, and is also used as one of G0 the chemical agentsnecessary for corrosion. A practically perfect mixture is obtained of asolid, liquid and a gas, the strength of the mixture or the percentageof the various chemical agents being subject to accurate regulation. Thelead oxide particles are exposed to all the corroding agentssimultaneously, thereby permitting the chemical reactions to take placeas tast as possible.

With this process, White lead is obtained directly from litharge or anylower oxide of lead or mixture of such oxides without employing anyother chemical agents than those now used for corroding any particular 7oxide; also white lead is produced in commercial quantities from thelead oxides in a matter ot a few minutes, a hitherto unheard o't'accomplishment and 100% corrosion of the oxide is obtained. White leadproduced according to this process is physi cally different and muc-hsuperior, as it has a greater opacity or hinding power than old Dutchwhite lead in the ratio of 18 to 10 and whiter than any white lead nowon the market; in fact, whiter than Zinc oxide.

Other objects, novel features and advantages of the invention will beapparent from the following specification and accompanying drawings,wherein Figure 1 discloses one type of apparatus for producing whitelead according to the invention; and

Fig. 2 discloses a modified form of apparatus.

Referring now to Fig. 1, 1() is tank having a downwardly convergingbottom and provided with a removable cover l1 through which a charge maybe introduced into the tank. Near the lower part oi" the tank 10 isprovided a valve control inlet 12 and near the top ot the tank isprovided a valve control outlet, 13. A pipe lll leads from the bottomot' the tank 10 to the inlet of a pump l5, the outlet of which isconnected by pipe 1G to a nozzle 1,7 projecting into the tank l0. A pipe18 leads from the pipe 16 to a storage tank not shown. Valves 19 and 20are provided in the pipe 18 and 16 so that liquid discharged from thepump may be directed into the cylinder throughf the jet or nozzle 17 ormay be diverted to the storage tank when corrosion is completed. A pipe21 leading from a Water supply is connected to the pipe 14 and iscontrolled by valve 22. By means of this connection, fresh `Water may becirculated through the system thoroughly to Wash out the corroded leadbetore recharging the apparatus.

In producing White lead with this apparatus, a charge of acidulatedWater and powdered anhydrous lead oxide or litharge is introduced intothe tank in a sullicient quantity to fill the bottom of the tank #10 upto the inlet 12 and the circulating system. Carbon dioxide gas is fedthrough the tank 10 at a rate suliicient to accomplish corrosion. Thepump 15 is started and the fluid mixture With Which the apparatus hasbeen charged is sprayed through the nozzle 1'? into the body of the tank10 thereby dillusing the litharge through a corrosive atmosphereconsistingr of aqueous vapor, acetic acid and carbon dioxide gas. ticlesand mist tall through the tank and are collected at the bottom thereoffrom whence they are carried to the pump and again forced up through thenozzle into the corroding atmosphere. lThis action is continued untilall the lead oxide has been corroded which takes place in a very shorttime. The valve 20 may then be closed and the valve 19 opened and theliquid containing What is nonr 100% White lead pumped to the storagetank Where it may be Washed and further treated in. the usual manner. Byoperating the valve 20 Water may be supplied to the tank 10 to becirculated through the apparatus to clean it and make it ready foranother charge.

An almost perfect mixture of very finely divided particles of lead oxideand the necessary corroding agents is continuously effected and theproportions may be so regulated that corrosion takes place inaremarkably short time. All parts .of the charge are evenly anduniformly subjected to the corroding action of the atmosphere in the'chamber so that corrosion progresses at a uniform rate throughout thecharge, giving a completely uniform product both as respects hydrationand carbonation, of the formula 2PbCO3.Pb(Ol-l)2. It is a Wellknown factthat in White lead when subjected to corroding gases for any length oftime as in the old processes, the percentage of carbonate is increasedand hydration decreased. ln our product, this is avoided and a: Whitelead composed of particles of substantially uniform analysis secured andone in which there are no overdone particles or tendency towardcrystalline growth.

With this process, litharge is converted di- The lead parrectly intoWhite lead Without the formation of any appreciably stable intermediateproducts. T he acetic acid, of Which there is only one-half to one percent, A by Weight of the litharge used, forms hydrated lead oxide fromthe litharge, but because this action takes place in a carbonatingatmosphere and the carbon dioxide has a greater allinity for hydratedlead oxide than has acetic acid,

hydrated lead carbonate is formed directly instead of a lead acetatebeing formed and then converted into carbonate.

rlhe apparatus disclosed in Fig. 2 operates upon substantially the sameprinciple as that disclosed in Fig. 1. In this modification, the inlet12 for the gas constitutes a nozzle and the inlet 17 for the mixture ofacidulated Water and litharge discharges directly in line With thenozzle. An agitator 23 is provided for keeping the litharge Well mixedWith the Water.

Experiments have shown that there is a great physical difference as Wellas a `certain difference in chemical analysis between White leadresulting from reactions taking place in the moist atmosphere of aceticacid and gas and White lead resulting from the same chemical agentsacting in a body of liquid through which a gas is passed. A betterproduct is produced more expeditiously and economically by repeated andthorough diusion of very fine particles of lead oxide through an aqueouscorroding atmosphere.

In describing our process, We have used acetic acid as the hydratingagent or cata'- lyst, for the reason that this agent is the onegenerally used in making White lead. HOW- ever,cther hydrating agentsmay be used, such as ammonium acetate, nitric acid and other agents,Which/Will produce similar chemical reactions. It is to be understoodthat, Where We have described or claimed the use of acetic acid as ahydrating agent, We do not limit ourselves thereto but include the useof other equivalent hydrating agents Within the scope of this invention.

Ywhatwe claim as new and desire to secure by Letters Patent of theUnited States is 1. The method of making corroded White lead whichcomprises passing powdered anhydrous lead oxide through a corrodingatmosphere of aqueous vapors, acetic acid and carbon dioxide.

2. The method of making corroded white lead which comprises spraying amixture of acidulated Water-'and powdered lead oxide through anatmosphere of carbon dioxide.

3. The method of making corroded white laad which comprises passingpowdered litharge repeatedly through a corroding atmosphere of aqueousvapor, acetic acid and carbon dioxide.

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5. The pmeess of fom yf e hewe signed om' specieetiem.

FRANK T. BMLEY. WLTLSN AUS'XEN.

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